The present disclosure relates to a nitride-based semiconductor light-emitting device, and to a method of manufacturing the same.
In recent years, as a semiconductor light-emitting device, for example, a light-emitting diode (Light Emitting Diode; LED) at a wavelength band ranging between blue and green colors that is used for general lighting, and a semiconductor laser (Laser Diode; LD) at a green wavelength band that is used for a laser display, a pointer, etc. have been developed. These semiconductor light-emitting devices use nitride-based compound semiconductors. A nitride-based semiconductor light-emitting device typically includes an active layer having an AlInGaN-based quantum well structure, and makes it possible to achieve emission of light at the green wavelength band by increasing a composition ratio of In in the active layer.
In contrast, in a case of an increase in the composition ratio of the In in the active layer, an issue of deterioration in light-emitting efficiency will occur due to an increased difference in a lattice constant between the active layer and a foundation layer, an increased lattice distortion of a crystal in association with such an increased difference, and degradation in crystalline property such as proliferation of crystal defects or dislocation, etc.
As a method of resolving such an issue, a semiconductor laser is disclosed that utilizes a new quantum structure in which the active layer includes quantum dots (for example, see NPTL 1 and PTLs 1 to 3). The active layer with use of the quantum dots achieves a small absolute amount of the lattice distortion, allowing for suppression of crystal deterioration caused by the lattice distortion. Further, the active layer with use of the quantum dots reduces extra charges that make no contribution to laser oscillation, making it possible to generate an optical gain efficiently.